TDA2009A

[Electron Tornado]

Greetings from a complete guitar amp noob.

Has anyone used a TDA2009A chip for a guitar amplifier? I searched the forum with no results. Here is the datasheet:

http://pdf1.alldatasheet.com/datasheet-pdf/view/25041/STMICROELECTRONICS/TDA2009A.html

Figure 13 is a schematic for a 10W amplifier. It calls for 4 ohm speakers, and I just happen to have a pair.

Also, will I need a pre-amp with this?

Thanks for any help.

[J M Fahey]

Had never seen it before, I use the TDA2005 which is a slightly more modern version.
It's basically two TDA2003(LM383) in a single package.
In theory they are *power* amps and *should* need a preamp, but by cheating a little, increasing gain, they can be driven straight by a guitar.
Craig Anderton's version is http://www.generalguitargadgets.com/richardo/practiceamp/craig.gif
They do not show exact values for R2 and R3 but a range of acceptable values which will vary gain.
Start with the original (datasheet) suggested ones, and increase R2 until your guitar drives it properly.
In a nutshell: lowering R3 or rising R2 (or doing both) will increase gain.
Don't overdo it, it's not a distortion pedal.
Also check: http://www.google.com/#hl=en&source=hp&q=tda2003+guitar+amplifier&aq=f&aqi=&aql=&oq=&gs_rfai=&fp=f7ea90535a21e769
You may want to read about different versions in: http://www.generalguitargadgets.com/richardo/practiceamp/index.html

[Electron Tornado]

Thanks for the reply and the links, JM, they've been helpful. I am looking at keeping the project to about 10 Watts and is designed to drive 4 Ohm speakers.

[Electron Tornado]

JM,

I took a look at the datasheet for the TDA2005 and it has basically the same circuit as the TDA2003. However, I have a question regarding the potentiometers, P3 and P4, from the TDA2005 figure 27. Those look like volume controls, but I don't understand why the schematic shows 4 connections. (Same situation exists in the TDA2003 schematic.)

Thanks again for your help.

[DJPhil]

JM,

I took a look at the datasheet for the TDA2005 and it has basically the same circuit as the TDA2003. However, I have a question regarding the potentiometers, P3 and P4, from the TDA2005 figure 27. Those look like volume controls, but I don't understand why the schematic shows 4 connections. (Same situation exists in the TDA2003 schematic.)

Thanks again for your help.

The center pin is a loudness tap, basically just a wire that usually sits at 40% or 50% of the full resistance. At a certain point on the volume control it starts boosting the low end to make the signal sound louder. If that seems like a crazy thing to do, keep in mind that the common application for this chip was car stereo.

I'll try and go over the whole input, someone correct me if I go astray. P1/P2 are tone controls for each channel (oddly separate, in practice they're likely ganged), P3/P4 are volume (also likely ganged in normal use), and P5 is the balance. The mildly complex RC networks sprinkled everywhere are designed to set the response of the tone and loudness controls. You could use LTSpice to simulate from the input to the 0.22uF DC blocking cap and get an excellent idea of the workings. In short, all that mess is effectively just a tone stack and balance control, and you can replace it with a simple balance/volume system for use with a guitar.

Attached a screen cap of Figure 27 so nobody has to go looking for the sheet.

Hope that helps.

[Electron Tornado]

Thanks, DJ,

I did understand which pots did what, but the fourth connection on the vol pots had me scratching my head.

[J M Fahey]

Hi Tornado.
Before you advance too far, let me remind you that TDA2009 and 2005 are *similar* but *not* the same.
To make a long story short, 2003 (and 2009) is optimized to the max for 12.6V, sacrificing some little details; while 2005 and others (2006/30/40/50/52)  work better with higher voltages, because they are "big op amps",  which 2003 and 2009 are not.
You should analize the internal circuit but it's beyond the point here.
The feedback nets are NOT the same.
Notice that the 2003 one is very low impedance and passes DC to ground !!!!! It's required by the internal circuit.

Also the 2003 input pin is NOT ground referenced.
So: use the 2003 values, not the 2005 one.
You have two guitar amps there; if you wish to use both , from a single 100K Log volume pot drive both inputs in parallel but each output should drive its own speaker.
Good luck.

[DJPhil]

Thanks, DJ,

I did understand which pots did what, but the fourth connection on the vol pots had me scratching my head.

Ah, no worries. I babble on quite often.

Before you advance too far, let me remind you that TDA2009 and 2005 are *similar* but *not* the same . . .

Good call, I didn't even look at that side of the schematic.  :duh

[Electron Tornado]

JM and DJ,

Thank you for taking the time to reply. The amp project is in the research stage and your posts have been helpful.

Thanks again.

[Electron Tornado]

To make a long story short, 2003 (and 2009) is optimized to the max for 12.6V, sacrificing some little details; while 2005 and others (2006/30/40/50/52)  work better with higher voltages, because they are "big op amps",  which 2003 and 2009 are not.

Not sure about the 2009 being optimized for 12.6V. The data sheet shows electrical characteristics given for Vs of 24V and 18V. I'm basing the design on a supply voltage of 24V. I came up with a JFET preamp using a J201, and am working on the power supply. Hope to have a schematic up in a day or two.

[Electron Tornado]

Here's the schematic minus the power supply. Comments, critiques, suggestions all welcome. 

One question - how do I determine the current requirement for the power supply? (I plan on using an unregulated power supply.)

[joecool85]

Yours was a bit large to read on my screen...and I have a 22" monitor!

Anyway, I shrunk it for you.

[Electron Tornado]

Oops, sorry about it being so huge. Thanks for the re-size.